Whether you’re planning to travel to Europe for the Olympics or beyond, there’s a challenge that not every traveler is aware of. I’m talking about whether credit cards that may not be accepted abroad.

Here’s what’s happening. Most of Europe has now moved to chip-enabled credit cards—also known as EMV cards. That means no more cards with magnetic strips that require a signature to authorize.

The problem is many American banks haven’t made the switch. But that doesn’t mean that magnetic stripe cards are now null and void. What that means is the vendor may not be aware that the card is still readable.

Some travelers have run into problems when they use automated machines, like a train ticket kiosk, that won’t accept a magnetic strip card. That’s when it pays to follow my advice, which is to talk to a human being! What a concept.